Hormones are synthesized in larger inactive forms and then are activated by enzymatic digestion. A recently described enzyme, PC4, has been found only in the testis. Its role in the testis is unknown, as is the hormone that it acts upon. The present study is designed to test for the presence of PC4 in human testicular tumors and to see if it has a role in tumor formation. During the coming year additional testicular tumors will be collected by the GCRC.